With communicating data through the Internet, there is a fear of the data being falsified or being viewed by a third party, and there is a problem of ensuring security of data.
There has been proposed a known technique for encrypting data in order to prevent falsification of data or viewing of data by a third party. For example, a communication apparatus X encrypts data using a public key of a communication apparatus Y, and sends the encrypted data to the communication apparatus Y. The communication apparatus Y decodes the encrypted data by a self-secret key and acquires the data. Consequently, a third party can be prevented from sneaking a look at data.